Had my periods on 10 dec finish on 17 dec had sex on 18 n 19th dec could i get pregnant i have a 28 day cycle and when can i take test?

Pregnancy's possible: A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test. If a woman gets her normal regular period, then she is not pregnant, and a test is not needed.